An LED control device disclosed in Document 1 (JP2014-197495A) is exemplified as a conventional solid-state light source lighting device. The LED control device (hereinafter, referred to as “related device”) disclosed in Document 1 includes: a low-beam LED array including one or more LEDs (Light Emitting Diodes); a high-beam LED array including two or more LEDs; and a conversion unit configured to supply a drive current to a series circuit of the low-beam LED array and the high-beam LED array. The related device further includes: a control unit configured to control the conversion unit such that a value of the drive current approaches a target value; and a plurality of bypass switches each of which is connected in parallel with a corresponding LED. The conversion unit includes a voltage regulation converter and a current regulation converter. The voltage regulation converter is a DC to DC converter, and is configured to convert an input voltage received from an on-vehicle battery into an intermediate voltage. The current regulation converter is a step-down chopper circuit, and is configured to convert the intermediate voltage into the drive current.
The control unit is configured to turn on (light) all LEDs of the low-beam LED array and the high-beam LED array by turning off all the bypass switches, thereby realizing a high-beam function. The control unit is configured to turn on LEDs of the low-beam LED array alone by turning off bypass switches each of which is connected in parallel with an LED included in the high-beam LED array, thereby realizing a low-beam function.
An input voltage supplied from an on-vehicle battery may drastically vary according to a state of charge of the battery and/or an operating state of a load (such as audio equipment and air conditioner equipped in the vehicle, for example) that receives electricity from the battery. For example, a voltage of a battery that is mounted on an automobile (or two-wheeled vehicle) and has a rated value of 12 V may vary within a range of 9 V to 16 V. The related device is configured to boost the input voltage by use of the voltage regulation converter of the conversion unit, and hence the related device can turn on (light) all the LEDs even when a reduction of the input voltage occurs. Incidentally, further downsizing of a solid-state light emitting device lighting device for use in an automobile (especially two-wheeled vehicle) is desired. However, the related device is required to include two kinds of converters, the step-up/step-down type voltage regulation converter and the current regulation converter, and hence is difficult to be further downsized.